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S cu turn (hg. 3 a) consisting of two bars placed at right angles to each other, with the 

 point of junction fully as wide as any part of the basal segment and perfectly calcified. The 

 basal segment slightly tapering to the carinal extremity, the occludent segment widening 

 considerably to the apex, which is obliquely truncated. The length of the occludent segment 

 is slightly more than twice that of the basal segment. 



Ter gum (fig. t,ó) of a triangular shape, with three ridges, terminating in three promi- 

 nences of unequal length. The longest forms the basal point; of the two others that at the 

 occludent margin is the shortest. In the angle between the latter two prominences the apex of 

 the scutum in younger specimens fits exactly. In older specimens, like that figured in fio-. 2, 

 there is a distinct interspace between the apex of the scutum and the tergum. The valve is 

 rounded at the umbo and shows a tracé of a fourth prominence on the carinal margin just 

 above the apex of the carina. 



Carina (fig. $c and 4). Much bowed, rather narrow, long; externally the central ridge 

 is flattened towards the apex; internally the valve is concave, the concavity nearly reaching 

 to the disc-like basal portion. The width of the carina remains almost the same over its 

 whole length, with the exception of the basal portion which widens and forms a spatula, as 

 figured in fig. 4. 



Peduncle short, cylindrical, one third the length of the capitulum at most. 



Size. The capitulum, in the largest specimen, is more than 10 mm. when measured 

 along the occludent margin and about 1 2 mm. when measured from the apex of the terooim 

 to the base of the carina. It is the largest of the known species of the genus. 



Mouth. Lab rum with the upper part bullate as in the other species of the genus; 

 crest with a row of small triangular teeth. Palpi smail, conical, moderately clothed with bristles. 



Mandibles (fig. 5). Much like those of the other species of the genus: rather 

 narrow, distance between the tips of the first and seconcl teeth slightly shorter than that 

 between the second tooth and the inferior angle. The inferior angle produced into an indistinct 

 doublé spine. 



M a x i 1 1 a e (fig. 6). Three large upper unequal spines and a fourth delicate one attached 

 to the base of the third. Notch neither very wide nor very distinct, bearing two pairs of slender 

 spines and a much stronger one half way to the beginning of the projecting inferior part. The 

 latter bears nine or ten spines of unequal length and strength. 



Ou ter max-illae (fig. 7) rather broad, general shape rounded-quadrangular. Covered 

 with longf bristles which moreover form a dense tuft all over the outer margin. 



Cirri. First cirrus separated by a wide interval from the second pair; short, with the 

 two rami unequal in length, though both consisting of seven segments. The segments are broad, 

 quadrangular and thickly paved with long and slender spines. The other cirri have very long 

 rami as well as pedicels. 



Ca u dal appendages small and narrow with a few long spines at their ends. 



H. M. S. "Siboga" took this fine species at: 



Stat. 262. December 18, 1899. Lat. 5°53'.8S., Long. i32°48'.S E. Depth 560 m. Bottom: solid 

 bluish-grey mud, upper layer softer and brown mud. In all 9 specimens. 



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